US4841938A - Device for determining the direction of flow - Google Patents

Device for determining the direction of flow Download PDF

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Publication number
US4841938A
US4841938A US07/098,405 US9840587A US4841938A US 4841938 A US4841938 A US 4841938A US 9840587 A US9840587 A US 9840587A US 4841938 A US4841938 A US 4841938A
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United States
Prior art keywords
flow
set forth
fluid
sensor element
signal
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Expired - Fee Related
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US07/098,405
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English (en)
Inventor
Wolfgang Weibler
Wolfgang Porth
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Mannesmann VDO AG
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Mannesmann VDO AG
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Assigned to VDO ADOLF SCHINDLING AG reassignment VDO ADOLF SCHINDLING AG ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: PORTH, WOLFGANG, WEIBLER, WOLFGANG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/01—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by using swirlflowmeter
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6842—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow with means for influencing the fluid flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters
    • G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00—Indicating or recording presence, absence, or direction, of movement
    • G01P13/02—Indicating direction only, e.g. by weather vane

Definitions

  • the present invention relates to a device for determining the direction of flow of a fluid of substantially directed flow, with known mass flow, having a flow straightener and a sensor element associated therewith which gives off electric signals.
  • the fuel injection of internal combustion engines is controlled as a function of the mass flow of the intake air.
  • a mass-flow measuring device which operates in accordance with the eletrothermal principle.
  • Such a measuring device is provided, for compensation of the temperature, with at least one temperature-measuring element and the mass-flow measuring device proper, the main component of which is an electrically heatable resistance element which is arranged in the mass flow.
  • the heat removed from this heating element is a measure of the mass flow, more heat being removed the stronger the mass flow is.
  • Such a mass-flow measuring device is very insensitive to the direction of the flow since, regardless of whether the flow is directed forward or backward, practically the same electric signal is given off, corresponding to the heat removed. In other words, with a known mass-flow measuring device one can merely determine the amount of the mass flow, but not its direction. It has now been found that in the intake system of internal combustion engines oscillations of the air column occur under certain operating conditions, they being superimposed on the constant flow so that a rapidly pulsating flow results therefrom. Depending on the rpm and the number of cylinders, the natural frequency of the oscillation is within the range of between 10 and 1000 Hz. Depending on the velocity of flow and the amplitude of oscillation, reverse flows occur for short periods of time. As a result of the principle of measurement of the mass-flow measuring device described above, reverse flows produce the same measurement signal as intake flows, so that in the final analysis too large an amount of fuel is fed to the engine.
  • Direction-sensitive flowmeters which have two resistance elements which are arranged on a common support and are installed one behind the other in the direction of flow. Such flowmeters, however, are not suitable, in view of their inertia, for the detecting of rapid changes in flow.
  • this object is achieved in the manner that sensor element (12) is sensitive to turbulence and is arranged in the path of flow between the flow straightener (32) and an eddy element (16).
  • the sensor element is exposed to a strongly turbulent flow when the fluid flows in the direction from the eddy element to the sensor element.
  • the sensor element In the reverse direction of flow, the sensor element is located within the undisturbed laminar flow of the fluid.
  • the sensor element gives off different electric signals depending upon whether it is exposed to laminar or turbulent flow.
  • the sensor element (12) is an electrically heated temperature-dependent resistance element (112).
  • This resistance element is cooled by the fluid which flows past it, the intensity and uniformity of the cooling being dependent on the state of flow of the fluid. While in the case of laminar flow completely constant cooling takes place, with turbulent flow there is a substantially more intense cooling action which varies with the frequency of the turbulences. Accordingly, with turbulent flow, high-frequency changes in resistance take place which are impressed as high-frequency modulation on the current conducted through the resistance element. It is therefore obvious that for such a measurement the resistance element must have extremely low thermal inertia in order not by itself to balance out the rapid variations.
  • the temperature-dependent resistance element can be arranged in a branch of a bridge circuit formed with three other fixed resistors, the bridge voltage experiencing a modulation which corresponds to the changes in resistance.
  • the resistance element In order to obtain a high signal level it is advantageous for the resistance element to consist of a metallic conductor such as nickel or platinum and therefore a metal of high positive temperature coefficient (PTC).
  • PTC positive temperature coefficient
  • the resistance element (112) may also be desirable for the resistance element (112) to have a negative temperature coefficient (NTC).
  • a rapid response of the resistance elements (112) is assured when they are developed in the form of wires.
  • the resistance element is arranged free-standing in the flow and the mass inertia, and thus the response time, of the resistance element can be controlled via the cross section of the wire.
  • wire there is to be understood here any elongated development of the resistor, whether its cross section is round, polygonal or flat. Particularly in the case of thin wires, which permit of rapid response, the mechanical strength must be taken into account.
  • resistance elements (112) in sheet shape, the resistance layer being applied onto a substrate of slight thermal capacitance and high temperature conductance.
  • Such resistance elements can, in particular, be integrated into miniaturized components.
  • the miniaturized embodiment has the advantage that the turbulent flow is detected at a point.
  • the small three-dimensional size of the resistance element furthermore has the advantage that there is no mean-value formation, in view of the small thermal capacitance.
  • a reproducible measurement signal is obtained if a regulating unit (50) is provided for adjusting the feed voltage of the bridge circuit for the setting of the measurement temperature of the temperature-dependent resistance element (112). In this way measurement is effected, both in the case of small mass flow and in the case of high mass flow, with the same temperature of the measurement resistor.
  • a signal of the mass-flow measuring device can, for example, be processed.
  • the measurement signal has a constant basic level on which the flow-affected modulation is impressed.
  • the resistance element is heated for a short time at an elevated feed voltage.
  • the device of the invention be connected to a known device for controlling the fuel injection for an internal combustion engine as a function of the mass flow of the quantity of air drawn in, the fuel metering being effected as a function of the signals of the sensor element (12) which are given off upon turbulent flow. In this way it is possible to reduce the excessively high feeding of fuel which takes place under given operating conditions, as soon as a reverse flow is noted in the intake system of the internal combustion engine by the device of the invention.
  • One particularly advantageous embodiment of the apparatus of the invention is present if the sensor element (12) is connected to the input of an amplifier (52) whose output is connected, via a Schmitt trigger (54), to the input (60) of a control unit (64) which, via a second input (62), is furthermore connected to a mass-flow measuring device (66) and is connected on the output side to a fuel metering device (70).
  • the measurement signal given off by a known mass-flow measuring device to a fuel metering device also known per se, is acted on in accordance with the invention by the correction signal given off by the device for determining the direction of flow.
  • Schmitt trigger (54) is connected to the mass-flow measuring device (66) for the adjustment of the level.
  • the Schmitt trigger (54) is connected for the adjustment of the level to a speed-of-rotation measuring device and/or a device for detecting the angle of opening of the throttle valve of an internal combustion engine.
  • the mass-flow measuring device and the device for determining the direction of flow are spaced apart from each other, it may happen that the signals of the two devices arrive shifted in time from each other. It is then advisable to arrange a phase shifter (56) between the output of the Schmitt trigger (54) and the input (60) of the control unit (64). If, in special cases, a period of time for influencing the measurement signal which is different from the duration of the correction signal is desired, then it is advantageous to arrange a monostable flip-flop (58) in front of the input of the control unit. In this way, a short incoming pulse can be correspondingly lengthened or else shortened.
  • the correction signal can act fundamentally in different ways on the measurement signal. In this connection it has been found advisable for a correction signal to be given off only when reverse flow takes place, i.e. for no signal to be given off to the control unit upon flow in the intake direction.
  • the correction signal can, in principle, act in three particularly advantageous ways on the measurement signal:
  • the control unit (64) can supress the measurement signal coming from the mass-flow measuring device (66) as long as a correction signal is present on the second input (60) of the control unit. In this simple way, the unnecessary and injurious over-feeding of the fuel can be avoided. It is self-evident that, specifically with such a device, an integrator which smooths the output signal is of particular importance.
  • the control unit (64) can substract the value of a measurement signal found during the duration of a correction signal present at the input (60) from that value of the measurement signal which is found within the period of time of the absent correction signal.
  • This theoretically correct influencing presupposes that both the mass flow and the direction of flow are determined completely without inertia and under identical measurement conditions. This result can be reached in practice only at great expense.
  • the mass-flow measuring device also has a certain integrating character since the air heated by the measurement element upon reverse flow passes again over the measurement element upon change to the normal direction of flow and thus cools it less. Accordingly, the following described control has proven economically the most logical.
  • the control unit (64) can reduce the value of the measurement signal found during the duration of a correction signal present on the input (60) to a predetermined fraction.
  • FIG. 1 is a diagrammatic view of the arrangement of one embodiment of the device of the invention.
  • FIG. 2 is a diagrammatic wiring diagram of a bridge circuit of the device of the invention with temperature-dependent resistors
  • FIG. 3 is a diagrammatic view of the circuit arrangement for the control of the fuel metering device as a further development of the device of the invention.
  • FIG. 1 shows diagrammatically the geometrical arrangement of a sensor element 12 between a flow straightener 32 and an eddy element 16 within a flow channel 10.
  • the sensor element 12 is shown diagrammatically as a temperature-dependent wire-shaped resistor seen in top view, it passing through the center of the mass flow flowing within the flow channel 10.
  • a flow straightener 32 which, as a honeycomb body, has numerous parallel flow channels.
  • an eddy element 16 in the form of a flat body which extends in longitudinal direction parallel to the sensor element. If the flow takes place, for instance, from left to right in the arrangement shown in FIG.
  • the flow first comes against the flow straightener 32, then against the sensor element 12, and finally against the eddy element 16. In this way assurance is had that the sensor element is always acted on by laminar flow.
  • the sensor element 12 lies in the eddy zone of the flow which is caused by the eddy element 16, the flow then passing through the flow straightener 32.
  • the sensor element 12, which is developed as an electrically heated temperature-dependent resistance element 112 is not as uniformly cooled in the turbulent flow as in the laminar flow. The electrical resistance of the resistance element thus changes corresponding to the eddy frequency.
  • the temperature-dependent resistance element arranged in the flow channel 10 is designated 112 and the fixed resistors of a bridge circuit are designated 42, 44 and 46, the resistors 112 and 46 as well as 42 and 44 being connected in each case as voltage dividers.
  • the feeding of the bridge circuit is effected via a variable voltage/current source 50.
  • a voltage difference occurs in the bridge diagonals at the measurement points between the resistors 42 and 44 and between the resistors 112 and 46. From this voltage difference there is formed, via an amplifier 52, a correction signal which, after passing through a high-pass filter 51, is fed to an integrator 53 for formation of the mean value.
  • the high-pass filter 51 is tuned to the turbulence frequency so that it permits passage only of those portions of the signal caused by the latter.
  • the feed voltage for the bridge circuit which is given off by the voltage source 50 is controlled as a function of the measurement signal of a mass-flow measuring device 66. In this way, the result is obtained that stronger heating of the resistance element 112 takes place with high mass flow than with small mass flow or, in other words, overheating of the resistance element 112 is prevented in the case of low mass.
  • the regulating of the temperature is effected in such a manner that the resistance element 112 takes on a constant positive difference in temperature as compared with the oncoming fluid.
  • FIG. 3 shows diagrammatically the further path of the correction signal given off by the amplifier 52 via the high-pass filter 51 and the integrator 53.
  • a Schmitt trigger 54 which serves as threshold switch, on the one hand, screens out signals which are too low, and on the other hand, forwards a constant signal regardless of the value of the input signal.
  • the output of the Schmitt trigger 54 is connected to an input 60 of a control unit 64.
  • the measurement signal of the mass-flow measuring device 66 is received at another input 62 of the control unit 64.
  • the output of the control unit 64 is connected to a fuel metering device 70.
  • the pulsations of the mass flow which lead to pulsating signals are smoothed by means of an integrator 68.
  • the Schmitt trigger 54 is connected to the mass-flow measuring device 66 in order to control the input level of the Schmitt trigger. With high mass flow, the input level of the Schmitt trigger is now raised to such an extent that turbulence signals below a certain threshold value are ignored.
  • a phase shifter 56 is provided which sees to the synchronizing of the signals.
  • a monostable flip-flop 58 which makes it possible to control the pulse duration of the correction signal differently from the pulse length of the input signal.
  • the control unit 64 has the task of adapting the signal given off to the fuel metering device, which signal is dependent primarily on the mass-flow measuring device, in accordance with the correction signal.
  • the measurement signal of the mass-flow measuring device which enters during this phase of the pulsation is suppressed by the control unit or subtracted from the value of the measurement signal entering during the rest of the phase or reduces the measurement signal to a fraction lying between the measured value and zero, the value of the fraction as well as of the speed of rotation of the engine being also dependent on the value of the mass flow.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Measuring Volume Flow (AREA)
  • Indicating Or Recording The Presence, Absence, Or Direction Of Movement (AREA)
  • Fuel-Injection Apparatus (AREA)
US07/098,405 1986-11-04 1987-09-17 Device for determining the direction of flow Expired - Fee Related US4841938A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3637540 1986-11-04
DE19863637540 DE3637540A1 (de) 1986-11-04 1986-11-04 Vorrichtung zur bestimmung der durchflussrichtung

Publications (1)

Publication Number Publication Date
US4841938A true US4841938A (en) 1989-06-27

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US07/098,405 Expired - Fee Related US4841938A (en) 1986-11-04 1987-09-17 Device for determining the direction of flow

Country Status (5)

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US (1) US4841938A (en, 2012)
EP (1) EP0266480B1 (en, 2012)
JP (1) JPS63122964A (en, 2012)
BR (1) BR8701745A (en, 2012)
DE (2) DE3637540A1 (en, 2012)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4913099A (en) * 1988-03-29 1990-04-03 Nissan Motor Co., Ltd. Fuel injection control apparatus
US5000039A (en) * 1989-11-21 1991-03-19 Siemens-Bendix Automotive Electronics L.P. Mass air flow integrator
US5085197A (en) * 1989-07-31 1992-02-04 Siemens Aktiengesellschaft Arrangement for the detection of deficiencies in a tank ventilation system
US5201322A (en) * 1988-08-17 1993-04-13 Elf Atochem North America, Inc. Device for detecting air flow through a passageway
US5329812A (en) * 1991-03-20 1994-07-19 Mitsubishi Denki Kabushiki Kaisha Thermal flow sensor
US5717136A (en) * 1994-02-28 1998-02-10 Unisia Jecs Corporation Hot film type air flow quantity detecting apparatus applicable to vehicular internal combustion engine
US6189380B1 (en) * 1998-03-19 2001-02-20 Mitsubishi Denki Kabushiki Kaisha Flow rate sensor
US6557409B2 (en) * 2000-06-05 2003-05-06 Siemens Aktiengesellschaft Mass flowmeter
US20060032481A1 (en) * 2004-08-11 2006-02-16 Jin-Hong Park Method for determining amount of fuel injection in engine system
US20080289411A1 (en) * 2007-05-21 2008-11-27 Abb Ag Thermal mass flow meter and method for its operation
WO2012050499A1 (en) * 2010-10-12 2012-04-19 Braennstroem Roland A method and an apparatus for indicating a critical level of a liquid flow
US20130068014A1 (en) * 2011-09-16 2013-03-21 Mitsubishi Electric Corporation Thermal flow sensor for vehicles
CN105909358A (zh) * 2015-02-20 2016-08-31 丰田自动车株式会社 内燃机的冷却装置
US10954879B2 (en) * 2017-10-27 2021-03-23 Continental Automotive France Method for adapting a fuel injector control signal

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0426973A (ja) * 1990-05-21 1992-01-30 Sony Corp テープカセット
DE102013019872B4 (de) * 2013-11-28 2023-03-30 Universität des Saarlandes Campus Saarbrücken Verfahren und Vorrichtung zur Bestimmung der Viskosität einer in einem Strömungskanal strömenden Flüssigkeit

Citations (8)

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US3147618A (en) * 1961-06-08 1964-09-08 Hastings Raydist Inc Fluid flow measuring apparatus
US3677085A (en) * 1970-04-08 1972-07-18 Yugen Kaisha Tsukasa Sokken Tandem-type hot-wire velocity meter probe
US3777563A (en) * 1970-12-26 1973-12-11 Yokogawa Electric Works Ltd Flow-velocity detecting device
US3975951A (en) * 1974-03-21 1976-08-24 Nippon Soken, Inc. Intake-air amount detecting system for an internal combustion engine
SU581400A1 (ru) * 1975-01-02 1977-11-25 Военно-Инженерная Ордена Ленина Краснознаменная Академия Им. В.В.Куйбышева Электротермоаномометрический преобразователь перепада давлений
US4083244A (en) * 1975-11-24 1978-04-11 Agar Instrumentation Incorporated Method and apparatus for measuring fluid flow and/or for exercising a control in dependence thereon
US4304129A (en) * 1978-11-13 1981-12-08 Nippon Soken, Inc. Gas flow measuring apparatus
JPS6126822A (ja) * 1984-07-16 1986-02-06 Mitsubishi Electric Corp 感熱式気体流量検出装置

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DE1224546B (de) * 1961-09-08 1966-09-08 Willy Neuerburg Dr Ing Richtungsempfindliche Hitzdrahtsonde
US3995481A (en) * 1973-02-07 1976-12-07 Environmental Instruments, Inc. Directional fluid flow transducer
DE2444511C3 (de) * 1974-09-18 1981-07-30 Volkswagenwerk Ag, 3180 Wolfsburg Thermischer Strömungsmesser für gasförmige Medien
JPS5921485B2 (ja) * 1979-09-17 1984-05-21 日産自動車株式会社 流速又は流量検出器
DE3009382A1 (de) * 1980-03-12 1981-09-24 Degussa Ag, 6000 Frankfurt Vorrichtung zur messung der stroemungsgeschwindigkeiten von gasen und fluessigkeiten
JPS604408B2 (ja) * 1980-11-19 1985-02-04 日産自動車株式会社 カルマン渦流量計

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3147618A (en) * 1961-06-08 1964-09-08 Hastings Raydist Inc Fluid flow measuring apparatus
US3677085A (en) * 1970-04-08 1972-07-18 Yugen Kaisha Tsukasa Sokken Tandem-type hot-wire velocity meter probe
US3777563A (en) * 1970-12-26 1973-12-11 Yokogawa Electric Works Ltd Flow-velocity detecting device
US3975951A (en) * 1974-03-21 1976-08-24 Nippon Soken, Inc. Intake-air amount detecting system for an internal combustion engine
SU581400A1 (ru) * 1975-01-02 1977-11-25 Военно-Инженерная Ордена Ленина Краснознаменная Академия Им. В.В.Куйбышева Электротермоаномометрический преобразователь перепада давлений
US4083244A (en) * 1975-11-24 1978-04-11 Agar Instrumentation Incorporated Method and apparatus for measuring fluid flow and/or for exercising a control in dependence thereon
US4304129A (en) * 1978-11-13 1981-12-08 Nippon Soken, Inc. Gas flow measuring apparatus
JPS6126822A (ja) * 1984-07-16 1986-02-06 Mitsubishi Electric Corp 感熱式気体流量検出装置

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4913099A (en) * 1988-03-29 1990-04-03 Nissan Motor Co., Ltd. Fuel injection control apparatus
US5201322A (en) * 1988-08-17 1993-04-13 Elf Atochem North America, Inc. Device for detecting air flow through a passageway
US5085197A (en) * 1989-07-31 1992-02-04 Siemens Aktiengesellschaft Arrangement for the detection of deficiencies in a tank ventilation system
US5000039A (en) * 1989-11-21 1991-03-19 Siemens-Bendix Automotive Electronics L.P. Mass air flow integrator
US5329812A (en) * 1991-03-20 1994-07-19 Mitsubishi Denki Kabushiki Kaisha Thermal flow sensor
US5717136A (en) * 1994-02-28 1998-02-10 Unisia Jecs Corporation Hot film type air flow quantity detecting apparatus applicable to vehicular internal combustion engine
US6189380B1 (en) * 1998-03-19 2001-02-20 Mitsubishi Denki Kabushiki Kaisha Flow rate sensor
US6557409B2 (en) * 2000-06-05 2003-05-06 Siemens Aktiengesellschaft Mass flowmeter
US20060032481A1 (en) * 2004-08-11 2006-02-16 Jin-Hong Park Method for determining amount of fuel injection in engine system
US7082929B2 (en) * 2004-08-11 2006-08-01 Hyundai Motor Company Method for determining amount of fuel injection in engine system
US20080289411A1 (en) * 2007-05-21 2008-11-27 Abb Ag Thermal mass flow meter and method for its operation
US7644612B2 (en) * 2007-05-21 2010-01-12 Abb Ag Thermal mass flow meter and method for its operation
WO2012050499A1 (en) * 2010-10-12 2012-04-19 Braennstroem Roland A method and an apparatus for indicating a critical level of a liquid flow
US20130068014A1 (en) * 2011-09-16 2013-03-21 Mitsubishi Electric Corporation Thermal flow sensor for vehicles
US8959995B2 (en) * 2011-09-16 2015-02-24 Mitsubishi Electric Corporation Thermal flow sensor having a power source for driving a bridge circuit and an integrated circuit
CN105909358A (zh) * 2015-02-20 2016-08-31 丰田自动车株式会社 内燃机的冷却装置
US9920681B2 (en) 2015-02-20 2018-03-20 Toyota Jidosha Kabushiki Kaisha Cooling apparatus for internal combustion engine
CN105909358B (zh) * 2015-02-20 2018-10-12 丰田自动车株式会社 内燃机的冷却装置
US10954879B2 (en) * 2017-10-27 2021-03-23 Continental Automotive France Method for adapting a fuel injector control signal

Also Published As

Publication number Publication date
JPH0569468B2 (en, 2012) 1993-10-01
EP0266480B1 (de) 1990-06-13
DE3637540A1 (de) 1988-05-05
EP0266480A1 (de) 1988-05-11
JPS63122964A (ja) 1988-05-26
BR8701745A (pt) 1988-06-14
DE3763260D1 (de) 1990-07-19

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